Hydraulic percussive drill



2 sheets-sheet 1 fuis .lldlv Jan. 20, 1970 R. K. CATTERSON HYDRAULI C PERO US S IVE .DRILL Filed Aug. 15, 1958 Jan. 20, 1970 R. K. CATTERSON HYDRAULIC PERCUSSIVE DRILL Filed Aug. l5, 1968 2 Sheets-Sheet 2 "QVENTOR I?. K. CGTTEEfQ/v BY .Y Mfr Afroamvavs 3,490,549 Y HYDRAULIC PERCUSSIVE DRILL Robert K. Catterson, Columbus, Ohio, assignor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Filed Aug. 13, 1968, Ser. No. 752,244 Int. Cl. B25d 9/04 U.S. Cl.l 173-134 10 Claims ABSTRACT OF THE DISCLOSURE A hydraulically actuated rock drill having percussive drilling action and provided with means for snubbing the hammer upon over-travel as well as means for minimizing the possibilities of cavitation in the piston and Valve areas.

RELATED PATENTS The present application is related to United States Patent No. 3,230,711, dated Jan. 25, 1966 to I ames C. Swain, George E. Manning, and David L. Thomas.

BACKGROUND In the drilling of rock and ore, it is customary to employ percussive drilling tools which utilize pressurized fluid for delivering a succession of impact blows to a striking element or hammer which, in turn, transmits the same to a drill steel chuck for performance of the work. In most instances, these devices have heretofore utilized pneumatic motors operable by compressed air as the power source. However, it has more recently been proposed to use percussive drills powered by hydraulic fluid under pressure and acting on a reciprocating piston to motivate the striker, and one such hydraulically actuated drill is shown and described in the above-identified patent.

In these hydraulically actuated percussive drills, the impact blows imparted to the striker or hammer are necessarily at a high velocity in order to perform the required work, and considerable shock is therefore encountered during reciprocation of the striker. This is, of course, particularly true when the drill steel is running loose or free and the striker tends to overtravel on the impact stroke. Means must accordingly be provided for snubbing the hammer and absorbing the shock during such overtravel, and while prior attempts have been made in this direction, they have not all proven entirely satisfactory for -various reasons.

Also, it has been found that cavitation in the vicinity of the actuating piston and valve areas has presented a rather severe problem in these hydraulically actuated devices. For example, the hammer or striker and the actuating piston come to an abrupt stop at the end of the return stroke, and the oil iowing out of the actuating piston chamber continues on from its own inertia, thus creating a vapor cavity in the vicinity of the piston. Upon shifting of the Valve, high pressure oil is admitted to the piston chamber, and this oil collapses the vapor bubbles and causes severe damage to the surrounding metal parts. This condition is particularly prevelant when drilling in hard rock when the return velocity of the striker or hammer is naturally higher, thus increasing the tendency of the, oil to separate from the piston at the end of the stroke and emphasizing the cavitation problem.

SUMMARY It is therefore an object of the present invention to provide improvements in hydraulically actuated percussive` drills of either the drifter or stoper type which obviate the aforesaid problems encountered with prior devices of this type.

"United States Patent O ice One important object of this invention is to provide a hydraulic percussive tool which embodies highly effective shock absorbing or cushioning means for snubbing the striker element upon overtravel thereof to thereby prevent the striker from impacting against the housing or casing.

Another important object of the invention is to provide improvements in hydraulically actuated percussive tools by means of which the cavitation problem resulting from the rapid transfer of actuating fluid in the piston and valve areas is greatly minimized.

Still another object of the invention is to provide an improved hydraulically actuated percussive drill wherein the hydraulic fluid is subjected to a throttling action as it is exhausted on the return stroke of the striking element and actuating piston to thereby increase the pressure of the actuating uid in the upstream passages and thus minimize the possible formation of cavitation bubbles while also utilizing the hydraulic lluid for effectively snubbing the striking element during overtravel.

These and other objects and advantages of the invention will become apparent from the following detailed description.

THE DRAWINGS A clear conception of the several features constituting the present invention and of the mode of operation of a typical hydraulically actuated drifter type drill embodying the improvements may be had by referring to the drawings accompanying and forming a part of this specication, wherein like reference characters designate the same or similar parts in the various views.

FIGURE 1 is a plan view of a typical drifter type rock drill embodying the features of the present invention;

FIGURE 2 is a longitudinal section through the drill taken along the line 2 2 of FIGURE 1 with the hammer and actuating piston at the end of a return stroke and about to commence an impact stroke;

FIGURE 3 is a section like that of FIGURE 2 but with the hammer and actuating piston at the end of an impact stroke and about to commence a return stroke;

FIGURE 4 is an end view of the drill taken from the rear;

FIGURE 5 is a transverse section through the drill taken along the line S-5 of FIGURE 2;

FIGURE 6 is another transverse section taken along the line 6-6 of FIGUREZ; and

FIGURE 7 is a fragmentary part-sectional view showing an alternate arrangement for returning the hammer.

DETAILED DESCRIPTION since the improvements may obviously be embodied to advantage in various types of hydraulic impact devices. Also, for a detailed description of the operation and control of the drill motor, the impacting and rotary modes of operation, the hydraulic system, and the operation of the uid llow control valve, reference is made to prior United States Patent No. 3,230,711 hereinabove fully identified.

In general, the hydraulic drifter drill shown herein as embodying the invention comprises, a main housing or casing 10 having essentially three sections, namely, a rear control and piston housing section 12, an intermediate striker or hammer conning section 14, and a front chuck and drill steel carrying section 16. The casing rsections 12, 14, and 16 are secured together in longitudinal alignment a suitable manner and are provided with axially alined bores 18, 20, and 22 respectively.

A chuck 26 is rotatably confined within the bore 22 of the front section 16, and a drill steel 28 having a work performing bit 30 is carried by the chuck 26 for rotation therewith and for axial sliding movement relative thereto. Mounted for reciprocatory movement within the bore of the intermediate casing section 14 is a striker or hammer 32 having a front nose portion 34 adapted to contact the adjacent rear portion 36 of the drill steel attachment or shank ybar upon movement of the striker in a forward direction. In turn, the striker or hammer 32 is motivated in a forward direction to thereby forcibly impact against the drill steel attachment 28 by means of a hydraulically actuated impact or actuating piston 38, the actuating piston 38 being slidably housed within a ported sleeve 40 secured in the bore 18 of the casing section 12.

Also housed within the rear casing section 12 is a control valve 44 which may be of the reciprocating spool type slidable within a ported sleeve 46 secured in a transverse bore 48 intersecting the rear end of the piston conning bore 18. The opposite ends of the transverse bore 48 are closed by members 50, 52, each of which carries a valve actuating pilot piston 54, 56, respectively, actuated by fluid pressure conducted through ports 58, 60 formed in the respective members 50, 52 dependent upon the position of the actuating piston 38 to shift the control valve 44.

The rear of the casing section 12 is closed by a cap 64 secured thereto as by means of machine screws 66, the adjacent faces of the casing section 12 and cap 64 being recessed to provide a chamber 68. Spanning the chamber 68 is an apertured wall-forming plate 70 which cooperates with a flexible diaphragm 72 to form an accumulator, the area 74 in back of the diaphragm being suitably pressurized as by a compressible gas. Pressurized hydraulic actuating iluid is admitted to the chamber 68 forwardly of the apertured wall 70 through an inlet port 76 and is selectively admitted to the spool valve chamber, as formed by the ported sleeve 46, through ports 78, 80 dependent upon the position of the valve spool 44.

Generally speaking, the percussive operation of the hydraulic drifter drill thus far described is similar to that of the stoper drill disclosed in Patent No. 3,230,711, and reference is made to such prior patent for a detailed description thereof. Briefly, pressurized hydraulic lluid is admitted via inlet port 76 under the control of an operator. The spool valve 44 is automatically positionable along the ported sleeve 46 by the pilot pistons 54, 56 which are actuated in response to the position of the actuating piston 38. With the valve 44 in the position shown in FIGURE 2, pressurized hydraulic fluid is admitted through ports 78, 80 and about the reduced portion of spool 44 to the rear face of piston 38 through port 82 in the sleeve 46. The piston 38 is thereby forcibly driven forwardly to impact upon the rear face of the striking element or hammer 32 which, in turn, forcibly impacts upon theend 36 of the drill steel attachment 28 to thereupon drive the same toward the work.

The spool valve 44 is operated automatically as follows: A constant pressure from the pressure source is maintained in conduit 60 and acts on the pin or piston 56 which is of lesser area than the pin or piston 54. When the piston 38 is at the beginning of the acceleration stroke as shown in FIGURE 2, it communicates this same pressure to the pin 54 of larger area through conduit 58 and thus drives the spool 44 to the position shown. When the desired acceleration has been attained, piston 38 communicates conduit 58 to exhaust, thusA releasing the pressure on pin 54. The spool 44 is thereupon driven to its limit of travel shown in FIGURE 3, and the underside or rear of the piston 38 is communicated to exhaust pressure to initiate the return stroke. The hammer 32 and actuating piston 38 may, of course, be returned to their starting positions either by means of a return spring as fully disclosed in the prior patent hereinabove referred to or hydraulically as shown herein. In operation, this cycle is constantly repeated with the actuating piston 38 and striking element 32 being reciprocated to impart a succession of percussive blows to the drill steel 28.

Inaddition to this percussive action, the drill steel may also be rotated as it performs its work. For this purpose, the chuck 26 is splined to a ring gear 88 which is rotatably supported in bearings 90, '92. The teeth 94 of ring gear 88 mesh with the teeth of a gear 96 driven through gears 98, by a suitable lluid motor 102. The hydraulic gear motor 102 may be operated to rotate the drill steel or shank bar 28 through the double reduction spur gear drive either independently of or simultaneously with its percussive operational mode, and for a more detailed description of the rotational mode, reference is again made to the above identified prior patent.

While the basic hydraulic system of the present device is similar to that previously used in thathigh pressure oil from the accumulator 68 passes through the automatic valve 44 to the actuating piston 38 which, in turn, accelerates the striker or hammer 32 and causes the same to impact against the drill rod 28, the striking element 32 in the present instance is returned by hydraulic pressure instead of by a mechanical spring. This is accomplished by applying a constant hydraulic pressure via port 78 and passageway 106 from the accumulator 68 to an annular area 108 of reduced diameter on the hammer 32, the annular reduced area 108 ybeing exposed to the passage 106 by way of an annular groove 110` in the wall 112 which communicates with ports 114 opening to an annular groove 116 in the sleeve 118 within which the hammer 32 is guided. Thus, with the pressure on the rear of the actuating piston 38 removed by the valve 44 when in the position shown in FIGURE 3, the iluid pressure acting on the annular shoulder 120 defining the reduced portion 108 of the hammer 32 returns the hammer, and thus the piston 38, to starting position as in FIGURE 2.

In addition, the present invention contemplates the provision of means for flooding the hammer cavity 124 with return pressure oil. To this end, the spool valve sleeve 46 is provided with a port 126 communicating with the hammer cavity 124 via passageway 128 and port formed in the wall 132 between the piston section 12 and hammer section 14, the llow through port 126 again being controlled by the automatic valve 44. Thus, as the hammer 32 and piston 38 are returned with the valve spool 44 moved toward the position shown in FIGURE 3, the port 126 is opened to permit oil from the actuating plston chamber to be discharged through the port 126, passageway 128 and port 130 to the hammer cavity 124. The hammer cavity is accordingly flooded with return pressure oil.

The present invention also contemplates the provision of means for snubbing the hammer 32 at the end of both the impact and the return stroke by throttling the oil between a portion of the hammer and the wall which defines the hammer cavity. To accomplish this snubbing action, the hammer 32 is formed with a rear head 134 of enlarged diameter, the rear peripheral edge of which is tapered as at 136 and the front peripheral edge of which is also tapered as at 138. The tapered rear edge 136 of the hammer head 134 extends outwardly beyond the port 130 and cooperates with the wall 132 to restrict llow through the port 130 to thus snub the hammer 32 upon its return stroke while also restricting and throttling the ilow of oil exhausted from the rear of the actuating piston 38 and through valve 44, port 126, passage 128 and port 130. The tapered front edge 138 of the hammer head 134 also acts as a snubber portion upon the forward stroke of the hammer 32 through cooperation with a similarly tapered annular portion 140 formed on the interior of the wall 112. Since the hammer cavity 124 is llooded with oil as aforesaid,v a certain amount of oil becomes trapped between the Cooperating tapered snubbing portions 138, 140 of the hammer head and the casing wall respectively upon the forward or impact stroke in the event of overtravel of the hammer 32. Excess oil is, of course, exhausted from the hammer cavity 124 through a discharge port 144, and some of the oil may be communicated to the sleeve 118 via ports 46, 48 for lubrication purposes.

An alternate arrangement for hydraulically returning the hammer to starting position at the end of each forward stroke is shown in FIGURE 7. In this modification, the hammer which is designated 152 is provided with an axial bore 154 for slidably confining a piston 156 which is extendable through the forward end 174 of the hammer. The bore 154 is placed in communication with the passageway 158 by way of an annular groove 160 in the wall 162 confining the hammer section, a port 164 in the sleeve 166 within which the hammer 152 is slidably confined, an annular inner groove 168 in the sleeve 166, land a port 170 communicating with the chamber 154. Piston 156 is subjected to source pressure independent of the position of the valve 44 in the same manner as hereinabove described with reference to the pin 56 with constant pressurized fluid being conducted via passageway 158, annular groove 160, ports 164, groove 168 and port 170 to chamber 154 rearwardly of the piston 156. Piston 156 is accordingly projected outwardly beyond the end 174 of the hammer 152 and into contact with the adjacent end of the drill rod 36. Thus, with the accelerating force removed as in FIGURE 3, the hammer and piston are driven to the initial position shown in FIGURE 7. As the hammer 152 moves forwardly on its impact stroke, a back pressure is exerted within the chamber 154 which provides suflicient force to return the hammer to its starting position as shown in FIGURE 3 at the end of each impact stroke.

By reason of the improved arrangement which causes the hammer cavity 124 to become flooded with return oil pressure as hereinabove described, coupled with the snubbing action provided by the tapered portion 136 of the head 134 of the hammer and the resultant throttling of oil through port 130, the oil pressure in the valve passages and in the actuating piston chamber is increased, thereby eliminating or at least minimizing any tendency for cavitation in these areas at the end of the return stroke. Also, by providing snubbing areas at both ends of the hammer head, the shocks attendant the hammer action are effectively absorbed, and the hammer is moreover ecectively snubbed by the cooperating tapered surfaces 138, 140 during overtravel on the impact stroke such as might be caused when the drill is freely reciprocating within a void or especially soft formations. The improved apparatus also provides for hydraulic return of the hammer and actuating piston to thereby eliminate the need for mechanical devices such as springs for effecting the return stroke.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. A percussive drill, comprising, a housing, a drilling tool slidable axially within said housing and having a work-performing portion extending therefrom, a striker slideably confined within said housing in axial alignment with said tool, an actuating piston slideably confined within said housing in axial alignment with said striker,

valve means communicable with a source of hydraulic fluid under pressure for alternately admitting and discharging pressurized hydraulic fluid to and from the end of said piston remote from said striker to actuate said piston and cause the striker to deliver a succession of impact blows to said tool, and means for throttling the hydraulic fluid as it is discharged by said valve means to thereby increase the pressure of the discharging fluid.

2. A percussive drill according to claim 1, wherein the striker is provided with the means for throttling the discharging hydraulic fluid.

3. A percussive drill according to claim 1, wherein a striker cavity is formed within the housing and the discharging hydraulic fluid is admitted to the striker cavity under control of the valve means.

4. A percussive drill according to claim 3, wherein the striker is formed with an enlarged portion confined for movement within the cavity and which provides the means for throttling the discharging hydraulic fluid.

5. A percussive drill according to claim 3, wherein the discharging hydraulic fluid is admitted to the striker cavity through a port in the end wall of the cavity.

6. A percussive drill according to claim 5, wherein the striker is formed with an enlarged portion having a tapered area adjacent the end wall port which provides the means for throttling the discharging hydraulic fluid.

7. A percussive drill according to claim 6, wherein the enlarged portion of the striker also has a tapered area remote form the end wall port which cooperates with an annularly tapered area of the striker cavity to resist movement of the striker toward the tool.

8. A percussive drill according to claim 5, wherein the valve means is an automatically operable spool valve movable from a position wherein pressurized hydraulic fluid is admitted to the end of the piston to initiate the impact movement to a position wherein the fluid is discharged from the end of the piston through the end wall port of the striker cavity.

3. A percussive drill according to claim 1, wherein the striker is formed with a reduced end portion remote from the actuating piston, and means is provided for conducting pressurized hydraulic fluid to said reduced end portion lo return the striker to starting position after delivery of each impact blow.

10. A percussive `drill according to claim 1, wherein the striker is provided with a pilot piston remote from the actuating piston, and means is provided for conducting pressurized hydraulic fluid to said pilot piston to cause the same to return the striker to starting position after delivery of each impact blow.

References Cited UNITED STATES PATENTS 3,230,711 1/1966 Swain 60-51 3,231,032 1/1966 Genberg z 173-134 X 3,314,488 4/1967 Brown et al. 173-134 X 3,322,210 5/1967 Arndt 173-134 3,371,726 3/ 1968 Bouyoucos 173-134 NILE C. BYERS, JR., Primary Examinerv U.S. Cl. X.R. 60-51 

